Compression Ratio questions

[1fast10]

Nice Coronet

 

[pokeytemplar]

You can kill a lot of STATIC compression with camshaft duration. I run pump gas in my Coronet with 11.5 compression, but the duration on the camshaft 268/276 @ .050 makes the dynamic compression (compression while running) 8.5 to 1. Here is a dynamic compression calculator that may help you.
http://www.speedwaybids.com/DynamicCompressionRatioCalculator.php

Very interesting, by increasing duration you are effectively reducing the amount of stroke that is used for compressing gases. Only the stroke/volume left after both valves are closed is counted in the dynamic compression ratio. So looking at Kyle's cam card his factory ratio of 9.5 is 7.38 dynamically.

Then what is the highest DYNAMIC compression ratio that can still run 93octane? Still 10:1 or significantly less?

 

[mopower1958]

your 67 coronet is really, nice I love that year because it is the year of the R/T,all you knowledge on motors is lucky for us, the indy motor is 13.1 comp higher?

Thanks for the compliment. No my Indy motor is only 11.5 compression. You can go as high as 15 to 1 static but you would have to use race gas.

 

[mopower1958]

Very interesting, by increasing duration you are effectively reducing the amount of stroke that is used for compressing gases. Only the stroke/volume left after both valves are closed is counted in the dynamic compression ratio. So looking at Kyle's cam card his factory ratio of 9.5 is 7.38 dynamically.

Then what is the highest DYNAMIC compression ratio that can still run 93octane? Still 10:1 or significantly less?

8.5 to 9 to 1 dynamic is about the limit. I have seen 12.2 static with a 286@ .050 cam run pump gas.

 

[pokeytemplar]

Very interesting, Now if that link you posted worked for me (website not the link specifically). I found another that did the same calculations but didn't include boost in to the formula.......